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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
<a name="id2476275"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>lwres_getipnodebyname, lwres_getipnodebyaddr, lwres_freehostent &#8212; lightweight resolver nodename / address translation API</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<div class="funcsynopsis">
<pre class="funcsynopsisinfo">#include &lt;lwres/netdb.h&gt;</pre>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
struct hostent *
<b class="fsfunc">lwres_getipnodebyname</b>(</code></td>
<td>const char *�</td>
<td>
<var class="pdparam">name</var>, </td>
</tr>
<tr>
<td>�</td>
<td>int �</td>
<td>
<var class="pdparam">af</var>, </td>
</tr>
<tr>
<td>�</td>
<td>int �</td>
<td>
<var class="pdparam">flags</var>, </td>
</tr>
<tr>
<td>�</td>
<td>int *�</td>
<td>
<var class="pdparam">error_num</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
struct hostent *
<b class="fsfunc">lwres_getipnodebyaddr</b>(</code></td>
<td>const void *�</td>
<td>
<var class="pdparam">src</var>, </td>
</tr>
<tr>
<td>�</td>
<td>size_t �</td>
<td>
<var class="pdparam">len</var>, </td>
</tr>
<tr>
<td>�</td>
<td>int �</td>
<td>
<var class="pdparam">af</var>, </td>
</tr>
<tr>
<td>�</td>
<td>int *�</td>
<td>
<var class="pdparam">error_num</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr>
<td><code class="funcdef">
void
<b class="fsfunc">lwres_freehostent</b>(</code></td>
<td>struct hostent *�</td>
<td>
<var class="pdparam">he</var><code>)</code>;</td>
</tr></table>
</div>
</div>
<div class="refsect1" lang="en">
<a name="id2543431"></a><h2>DESCRIPTION</h2>
<p>
      These functions perform thread safe, protocol independent
      nodename-to-address and address-to-nodename
      translation as defined in RFC2553.
    </p>
<p>
      They use a
      <span class="type">struct hostent</span>
      which is defined in
      <code class="filename">namedb.h</code>:
    </p>
<pre class="programlisting">
struct  hostent {
        char    *h_name;        /* official name of host */
        char    **h_aliases;    /* alias list */
        int     h_addrtype;     /* host address type */
        int     h_length;       /* length of address */
        char    **h_addr_list;  /* list of addresses from name server */
};
#define h_addr  h_addr_list[0]  /* address, for backward compatibility */
</pre>
<p>
    </p>
<p>
      The members of this structure are:
      </p>
<div class="variablelist"><dl>
<dt><span class="term"><code class="constant">h_name</code></span></dt>
<dd><p>
              The official (canonical) name of the host.
            </p></dd>
<dt><span class="term"><code class="constant">h_aliases</code></span></dt>
<dd><p>
              A NULL-terminated array of alternate names (nicknames) for the
              host.
            </p></dd>
<dt><span class="term"><code class="constant">h_addrtype</code></span></dt>
<dd><p>
              The type of address being returned - usually
              <span class="type">PF_INET</span>
              or
              <span class="type">PF_INET6</span>.

            </p></dd>
<dt><span class="term"><code class="constant">h_length</code></span></dt>
<dd><p>
              The length of the address in bytes.
            </p></dd>
<dt><span class="term"><code class="constant">h_addr_list</code></span></dt>
<dd><p>
              A
              <span class="type">NULL</span>
              terminated array of network addresses for the host.
              Host addresses are returned in network byte order.
            </p></dd>
</dl></div>
<p>
    </p>
<p><code class="function">lwres_getipnodebyname()</code>
      looks up addresses of protocol family <em class="parameter"><code>af</code></em>
      for the hostname <em class="parameter"><code>name</code></em>.  The
      <em class="parameter"><code>flags</code></em> parameter contains ORed flag bits
      to specify the types of addresses that are searched for, and the
      types of addresses that are returned.  The flag bits are:

      </p>
<div class="variablelist"><dl>
<dt><span class="term"><code class="constant">AI_V4MAPPED</code></span></dt>
<dd><p>
              This is used with an
              <em class="parameter"><code>af</code></em>
              of AF_INET6, and causes IPv4 addresses to be returned as
              IPv4-mapped
              IPv6 addresses.
            </p></dd>
<dt><span class="term"><code class="constant">AI_ALL</code></span></dt>
<dd><p>
              This is used with an
              <em class="parameter"><code>af</code></em>
              of AF_INET6, and causes all known addresses (IPv6 and IPv4) to
              be returned.
              If AI_V4MAPPED is also set, the IPv4 addresses are return as
              mapped
              IPv6 addresses.
            </p></dd>
<dt><span class="term"><code class="constant">AI_ADDRCONFIG</code></span></dt>
<dd><p>
              Only return an IPv6 or IPv4 address if here is an active network
              interface of that type.  This is not currently implemented
              in the BIND 9 lightweight resolver, and the flag is ignored.
            </p></dd>
<dt><span class="term"><code class="constant">AI_DEFAULT</code></span></dt>
<dd><p>
              This default sets the
              <code class="constant">AI_V4MAPPED</code>
              and
              <code class="constant">AI_ADDRCONFIG</code>
              flag bits.
            </p></dd>
</dl></div>
<p>
    </p>
<p><code class="function">lwres_getipnodebyaddr()</code>
      performs a reverse lookup of address <em class="parameter"><code>src</code></em>
      which is <em class="parameter"><code>len</code></em> bytes long.
      <em class="parameter"><code>af</code></em> denotes the protocol family, typically
      <span class="type">PF_INET</span> or <span class="type">PF_INET6</span>.
    </p>
<p><code class="function">lwres_freehostent()</code>
      releases all the memory associated with the <span class="type">struct
      hostent</span> pointer <em class="parameter"><code>he</code></em>.  Any memory
      allocated for the <code class="constant">h_name</code>,
      <code class="constant">h_addr_list</code> and
      <code class="constant">h_aliases</code> is freed, as is the memory for
      the <span class="type">hostent</span> structure itself.
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2543689"></a><h2>RETURN VALUES</h2>
<p>
      If an error occurs,
      <code class="function">lwres_getipnodebyname()</code>
      and
      <code class="function">lwres_getipnodebyaddr()</code>
      set
      <em class="parameter"><code>*error_num</code></em>
      to an appropriate error code and the function returns a
      <span class="type">NULL</span>
      pointer.
      The error codes and their meanings are defined in
      <code class="filename">&lt;lwres/netdb.h&gt;</code>:
      </p>
<div class="variablelist"><dl>
<dt><span class="term"><code class="constant">HOST_NOT_FOUND</code></span></dt>
<dd><p>
              No such host is known.
            </p></dd>
<dt><span class="term"><code class="constant">NO_ADDRESS</code></span></dt>
<dd><p>
              The server recognised the request and the name but no address is
              available.  Another type of request to the name server for the
              domain might return an answer.
            </p></dd>
<dt><span class="term"><code class="constant">TRY_AGAIN</code></span></dt>
<dd><p>
              A temporary and possibly transient error occurred, such as a
              failure of a server to respond.  The request may succeed if
              retried.
            </p></dd>
<dt><span class="term"><code class="constant">NO_RECOVERY</code></span></dt>
<dd><p>
              An unexpected failure occurred, and retrying the request
              is pointless.
            </p></dd>
</dl></div>
<p>
    </p>
<p><span class="citerefentry"><span class="refentrytitle">lwres_hstrerror</span>(3)</span>
      translates these error codes to suitable error messages.
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2543786"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry"><span class="refentrytitle">RFC2553</span></span>,

      <span class="citerefentry"><span class="refentrytitle">lwres</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">lwres_gethostent</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">lwres_getaddrinfo</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">lwres_getnameinfo</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">lwres_hstrerror</span>(3)</span>.
    </p>
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